In recent years, more and more electronic devices such as tablet personal computers and portable digital assistants include touchscreens to improve operability and usability. When a user touch a display surface of a liquid crystal panel with a finger or a stylus, position information in a display surface of the liquid crystal panel is entered. This provides the user with intuitive operation, that is, direct feeling as if he or she touches an image displayed on the liquid crystal panel. Examples of such touchscreens include touchscreens disclosed in Patent Document 1 and Patent Document 2.
Patent Document 1 discloses a self-capacitance touchscreen including a sensing path layer and an eliminating path layer. The sensing path layer includes multiple first paths and multiple second paths. The eliminating path layer includes multiple third paths. According to the configuration, real coordinates of multiple touched points can be determined. Patent Document 2 discloses compensations of pixels included in a touch sensor panel that generate erroneous readings (so-called “negative pixels”) due to a poor grounding condition of the object that touches the touch sensor panel in a mutual-capacitance touchscreen. Patent Document 3 discloses a method using a combination of a self-capacitance method and a mutual-capacitance method. A mutual-capacitance touchscreen is configured to scan first-axis electrodes arranged along a first axis and second-axis electrodes arranged along a second axis by a controller, to obtain the first-axis electrodes and the second-axis electrodes whose self-capacitances have changed, to determine a mutual-capacitance at each intersection of the first-axis electrodes and the second-axis electrodes whose self-capacitances have changed, to determine whether the mutual-capacitance has changed, and to determine an area in which the mutual-capacitance has changed as a contact area.